Method and apparatus for introducing a flocculating agent to an asbestoscement slurry to control the thickness of the sheet used in winding to form a pipe



Feb. 13, 1968 G. E. DE LONG 3,368,936

METHOD AND APPARATUS FOR INTRODUCING A FLOCCULATING AGENT TO ANASBESTOS-CEMENT SLURRY TO CONTROL THE THICKNESS OF THE SHEET USED INWINDING TO FORM A PIPE Original Filed April 16, 1964 5 Sheets-Sheet l M65 INVENTOR.

EOPEE Dela/g P .4 BY

ATTORNEY Feb. 13, 1968 'G. E. DE LONG 3,368,936

METHOD AND APPARATUS FOR INTRODUCING A FLOCCULATING AGENT TO ANASBESTOS-CEMENT SLURRY TO CONTROL THE THICKNESS OF THE SHEET USED INWINDING TO FORM A PIPE Original Filed April 16, 1964 3 Sheets-Sheet 2INVENTOR. 9 555 DE L 0&5

W a. ARK? A r TOE'A/E G. E. DE LONG METHOD AND APPARATUS FOR INTRODUCINGA FLOCCULATING Feb. 13, 1968 AGENT TO AN ASBESTOS-CEMENT SLURRY TOCONTROL THE THICKNESS OF THE SHEET USED IN WINDING TO FORM A PIPEOriginal Filed April 16, 1964 5 Sheets-Sheet 5 INVENTOR. geokgt-E.Dsloug BY United States Patent Ofitice 3,363,936 Patented Feb. 13, 1968METHOD AND APPARATUS BUR INTRODUCING A FLOCCULATING AGENT TO ANASBESTGS- CEMENT SLURRY T CONTRQL THE THICK- NESS OF THE SHEET USED INWINDING Tl) FORM A PIPE George E. De Long, Denison, Tern, assignor to.lohus- Manville Corporation, New York, N.Y., a corporation of New YorkContinuation of application Ser. No. 360,265, Apr. 16, 1964. Thisapplication Mar. 17, 1967, Ser. No. 624,683

8 Claims. (Cl. 162-118) This application is a continuation of Ser. No.360,265, filed Apr. 16, 1964, now abandoned.

This invention relates to the manufacture of products from a sheet ofparticulate material which is formed by the deposition of particulatematerial from a slurry onto a conveyor and more specifically to theintroduction of a flocculating agent into the slurry for controlling thedeposition of such particulate material onto the conveyor. Inparticular, the invention relates to the introduction of a flocculatingagent into an asbestos-cement slurry from which asbestos-cement pipe isformed.

In the formation of asbestos-cement products, especially asbestos-cementpipe wherein a sheet of asbestos-cement stock carried by an endlessconveyor is wrapped around a mandrel, there are many problems associatedwith maintaining the desired thickness of stock across the width of theconveyor so that asbestos-cement pipe of desired wall thicknesses andprofile will be formed. If it is desired to build a laminate ofsubstantially even thickness throughout its axial length on the mandrel,it might happen that for some reason or other associated with themanufacturing process more asbestos-cement stock is being consistentlydeposited on one side of the endless conveyor so as to build up one sideof the laminate on the mandrel to a thickness greater than the thicknessof the laminate on the other side of the mandrel. Also in someinstances, such as where better flex strength is desired, it isdesirable to form a laminate on the mandrel wherein a thicker portion ofthe laminate occurs at approximately the middle section of the mandrel.Many attempts have been made in the past to control the thickness of thelaminate during its formation on the mandrel by regulating the flow ofslurry over the flow pan prior to its entry into the mixing vat. Suchdevices as movable dams, separate feedings of the slurry, oscillatingfans, all function to produce some control of the formation of thelaminate on the mandrel. However, past experience has proven that evenwith such devices, the constant formation of the desired 'wall thicknesson the mandrel was extremely difi'icult or not at all possible toattain.

It is an object of the instant invention to provide method and apparatusfor controlling the deposition of particulate material from a slurryonto a conveyor so that the sheet of such deposited particulate materialon the conveyor will be of the desired thickness across the widththereof.

It is a further object of the instant invention to provide method andapparatus for the dispersing of a fiocculating agent into anasbestos-cement slurry so as to control the deposition ofasbestos-cement stock from such slurry on a conveyor so that thelamination of such asbestos-cement stock on a mandrel will be of thedesired thickness from one end to the other end thereof.

The foregoing objects are accomplished in accordance with the instantinvention by method and apparatus wherein a fiocculating agent isdispersed or deposited into a slurry prior to the deposition ofparticulate material from such slurry onto a conveyor. In the preferredembodiment of the invention, the fiocculating agent is introduced intoan asbestos-cement slurry as it is flowing Over the flow pan to bedeposited into the mixing vat of a conven tional asbestos-cement pipeforming machine. In the preferred embodiment of the invention, the flowpan is provided with a plurality of baflles so as to provide the surfaceof the flow pan with a plurality of channels which diverge from themouth portion of the flow pan which is adjacent the trough to the exitportion of the flow pan adjacent the mixing vat. Apparatus, which in thepreferred embodiment of the invention comprises a plurality of swivellymounted nozzles, is utilized to disperse a flocculating agent, such asone of the types described in Sfiscko et al., US. Patent No. 3,095,346,into the asbestoscement slurry as it passes over the flow pan. Theflocculating agent is dispersed into the flow pan so that a majorportion of the flocculating agent is deposited into that section of themixing vat where the increase in thickness of the laminate on theconveyor is most desired. Thus, if it is desired to have the thicknessof the middle section of the laminate on the conveyor increased, theapparatus would be positioned so that the major portion of theflocculating agent is dispersed into those channels adjacent the centralportion of the flow pan.

The invention will be more fully understood and further objects andadvantages thereof will become apparent when reference is made to thefollowing detail description of a preferred embodiment of the inventionand the accompanying drawings in which:

PEG. 1 is a side elevation of apparatus, schematically illustrated, madein accordance with the instant invention;

FIG. 2 is a pictorial represer-tation of a flow pan and dispersingsystem as illustrated in FIG. 1;

FIG. 3 is an end view of part of the flow pan; and

FIGS. 4 through 9 are pictorial representations of the flocculatingagent dispersing system in various positions; and

FIG. 10 is a schematic illustration of another form of the invention.

Referring to the drawings and in particular to FIG. 1, there isillustrated a portion of the apparatus used to manufactureasbestos-cement pipe for laminating a plurality of layers ofasbestos-cement stock on a mandrel. The general system for this type ofasbestos-cement manufacture is described in U.S. Patent No. 2,182,353 toRernbert. In FIG. 1, there is illustrated that portion of the Rembertpipe machine comprising a trough 2 having the base 4 and a pair of sidewalls 6. At one end the trough 2 is provided with a baffle 8 whichextends across the trough 2 and over which an aqueous slurry 10 flows.In the preferred embodiment of the invention the aqueous slurry 10comprises asbestos, cement and appropriate filler material such assilica mixed with a sufiicient quantity of water to form a slurry ofpredetermined viscosity. Spaced a short distance from the baffle 8 butextending generally parallel thereto and across the full Width of trough2 between the walls 6 is a gate valve comprising a lower element 12above which the gate 14 is positioned. The gate 14 is pivotally mountedat 16 and may be secured at desired locations so as to vary the opening18 between the top of the element 12 and the bottom of the gate 14 so asto control the amount of slurry flowing through the trough 2 and overthe bafile 8.

A flow pan 20 has one end 22 thereof in contact With the bottom ofbafiie 8 and the other end 24 thereof positioned over the back vat 26.The flow pan 20 diverges in a direction from the end 22 to the end 24and is positioned so that end 22 is higher than the end 24 to provide agravity feed. In the preferred embodiment of the invention, the angle ofdivergence is such that the width of the end 24 in a directionperpendicular to the flow of material over the flow pan 29 is aboutseven times greater than the corresponding width of the end 22. Theupper surface of the flow pan 20 is provided with a plurality of baffles28 which form channels 30 which diverge in proportions corresponding tothe divergence of the flow pan 20. In the preferred embodiment of theinvention, as illustrated in FIG. 3, each baffle 28 comprises aninverted angle section 32 secured by the welds 34 to the flow pan 2G.The flow pan 2% is also provided with edges 36 which extend upwardlyfrom the fiow pan 2. distance greater than a height of the anglesections 32 and which cooperate to hold the slurry in proper position asit flows over the flow pan 20.

The slurry flows over the end 24 of the flow pan into the back vat 26.In the bottom of the vat 26, there are agitators 38 for maintaining thesolid particles in suspension. A cylinder mold 41 is mounted forrotation in the back vat 26 and the aqueous slurry passing through 21facing wire on the cylinder mold deposits a thin sheet of solidmaterial, which as stated above in the preferred embodiment of theinvention comprises asbestos and cement, on the surface of the wire.This thin sheet is continuously transferred from the cylinder mold to anendless belt 42 which contacts the cylinder mold as it passes betweenthe cylinder mold and couch roll 44. Adjacent to the back vat 26 is thefront vat 46 having two agitators 48 therein for maintaining the solidparticles in suspension. A cylinder mold 50 is mounted for rotation inthe front vat 46 and the aqueous slurry passing through a facing wire onthe cylinder mold 5t} deposits a thin sheet of solid material on thesurface of the wire. This thin sheet is continuously transferred fromthe cylinder mold to the endless belt 42 which contacts the cylindermold 56 as it passes between the cylinder mold and couch roll 52. As isreadily apparent from FIG. 1, the sheet of asbestos-cement stock whichis carried by the endless belt 42 and from which the asbestos-cementproduct is formed comprises the composite laminate formed by the thinsheets of asbestos-cement deposited on the belt 42 by the cylinder molds56 and 40.

The mechanism which disperses the fiocculating agent, as illustrated inthe drawing, comprises a piping system 60 which is connected at one end62 with a pump (not shown) which feeds the flocculating agent to thepiping system and at its other end with a plurality of nozzles 64 and 65through which the flocculating agent 66 flows to be deposited in theasbestos-cement slurry as it flows over the surface of the flow pan 20.The first section of the piping system 60 comprises a. pair of swiveljoints 68 and 7t) joined by a pipe 72 which is generally maintainedsubstantially parallel to the upper surface of the flow pan 20. Theswivel joints 68 and are of a nature that they may be turned through 180for a purpose to be described. After the swivel joint 70, the pipingsystem 60 is provided with a T 74 which divides the flow of theflocculating agent through the first section of the pipe system into twoparts so that one part flows through the pipe 78 and the other partflows through the pipe 80. Between the pipe 78 and the nozzle 64, thereis provided a swivel joint 82 and between the pipe 80 and the nozzle 65there is provided a swivel joint 84. The pipes 78 and 80 are generallymaintained substantially parallel to the surface of the flow pan 20 andsubstantially perpendicular to the direction of the fiow of the slurryover the flow pan 20. The swivel joints 82 and 84 are of a nature thatthey may be rotated through 360 for a purpose to be described.

As illustrated in FIG. 1, the piping system 60 is positioned so that thenozzles 64 and 65 will disperse the fiocculating agent onto the flow pan20 at the location near the baffle 8. This section is sometimes referredto as the mouth of the flow pan. In forming asbestos-cement productsutilizing the apparatus illustrated in the drawings, an aqueous slurrycomprising asbestos, cement, and suitable fillers including silica isformed in the trough 2 in such a manner that the slurry flows over theelement 12 through gate valve 14 formed by the gate 14 and the element12 in an amount governed by the position of the gate 14-. The slurrythen flows over the baffie 8 and onto the end 22- of the flow pan 20.The amount of the slurry provided to the baffle 8 is sufficient toinsure that a substantially even flow of the slurry across the width ofthe battle 8 is obtained. As the slurry is deposited onto the flow pan20, it is divided into predetermined portions by the baflies 28 so as toflow over the flow pan 20 in the channels 30 and into the back vat 26.

In the manufacture of asbestos-cement pipe, a considerable decrease information time can be obtained by including in the slurry flocculatingagents such as those described and illustrated in Sfiscko et al., supra.In the commercial utilization of the process described in Sfiscko etal., it has been a general practice to include the fiocculating agent byadding it to the water immediately prior to the introduction of the drymixed materials such as asbestos, cement and fillers. In accordance withthe discovery of the instant invention, significant results incontrolling the wall thickness of asbestos-cement pipe made by a pipeforming process such as illustrated in Rembert, supra, may be obtainedby the addition of the flocculating agent at predetermined positions onthe surface of the flow pan and then controlling the movement of theslurry prior to its deposition into the mixing vat. In accordance withthe invention, the system for introducing the flocculating agent inamounts as set forth in Sfiscko et al., comprises the piping system 60through which the fiocculating agent flows so as to be deposited intothe slurry on the surface of the flow pan 20 by the nozzles 64 and 65.The exact position where the flocculating agent is dispersed into theslurry on the surface of the flow pan 20 is governed by suitablymanipulating the pipes 72, 78, and 80 and the nozzles 64 and 65 throughthe swivel joints 68, 70, 82, and 84. Various locations of theseelements are illustrated in FIGS. 4-9, inclusive, of the drawings. It isnoted that the swivel joints 6% and 72 function so that pipes 78 and $0may be moved from one side of the flow pan 20 to the other side thereofand still remain substantially perpendicular to the direction of theflow of the slurry over the flow pan 20. The swivels 82 and 84 allow thenozzles 64 and 65 to be rotated as desired so that they may be properlypositioned at desired locations over the flow pan.

By diverting or adjusting the point of introduction of the fioceulatingagent into the slurry, it is possible to correct any undesirablecharacteristics in the wall thickness of the pipe as it is being formedon the mandrel from the asbestos-cement stock carried by the endlessbelt in the pipe forming process. In addition to being able to correctfor the variations in wall thickness during the formation ofasbestos-cement pipe due to the peculiar characteristics of the pipeforming process itself, the instant invention makes it possible toprovide a predetermined control for governing the formation of a desiredwall thickness in particular sections of the laminate on the mandrel.Thus, in the manufacture of small diameter pipe where it is generallydesirable to increase the fiex strength of the pipe, the fiocculatingagent dispersing system is adjusted so that the floceulating agent isdeposited adjacent the central portion of the flow pan, such asillustrated in FIG. 5, so as to manufacture pipe having a greaterthickness in the center thereof as compared to the ends thereof. Thisprovides the pipe with greater flex strength without completelyjeopardizing its hydro strength. On a large diameter pipe where hydrostrength is a more essential factor in the control and acceptance of thepipe, the piping system 60 is adjusted to provide for maximum hydrostrength. This is achieved by an almost perfect lamination, in so far asthickness is concerned, from end to end of the pipe. This uniformity ofthickness is generally obtained by adjusting the nozzles 64 and 65 sothat they disperse the flocculating agent onto the surface of the flowpan 20 at distances equally spaced from the sides 36 of the flow pan 20,as illustrated in FIGS. 2 and 4. However, if for some unknown reason thepipe is formed with a greater thickness near one end thereof, this maybe corrected by moving the piping system to one side or the other suchas illustrated in FIGS. 8 and 9. In other instances control of the wallthickness of the pipe may be obtained by movement of the nozzles 64 and65 through the swivel joints 82 and 84 as illustrated in FIGS. 6 and 7.

In the form of the invention illustrated in FIG. 10, the flocculatingagent is introduced into the mixing vat 26 at the approximate locationwhere the slurry flows into the vat 26 from the flow pan 20. As noted inFIG. 10, the flocculating agent dispersing system 60 is located directlyabove the section of the mixing vat 26 adjacent the end of the flow pan20. It is understood that other flocculating agent dispersing systems,such as a plurality of individually controlled nozzles located acrossthe full width of the mixing vat, adjacent the section Where the slurryenters the vat, could be substituted for the flocculating agentdispersing system 60. The apparatus illustrated in FIG. is generallysimilar to that apparatus illustrated in FIG. 1 and corresponding partshave been similarly numbered. Also, the remaining portions of the pipeforming machine as disclosed in Rembert, supra, have been illustrated inFIG. 10.

The mixing vat 26 in FIG. 10 has been provided with a bafile 90 so thatthe slurry as it is deposited into the vat 26 must move downwardly andbe acted on by the agitator 38 prior to its entering the main body ofthe vat 26 where the asbestos-cement material in the slurry is depositedon the cylinder mold 40. The dispersing system 60 is positioned so thatit may disperse the flocculating agent into that portion of the vat 26between the bafiie 90 and the wall of the vat 26 in contact with the end24 of the flow pan 20. It is understood that the operation of thedispersing system 60 is similar to the operation described relative toFIG. 1. It is also to be noted that the flocculating agent dispersingsystem 60 of FIG. 10 may be moved to positions over the vat 26, similarto the positions illustrated in FIGS. 4-9, inclusive, to control by thedispersion of the flocculating agent at selected locations thedeposition of the particulate asbestos-cement material in the slurry inthe vat onto the cylinder molds 40 and 50 and the conveyor belt 42.

As illustrated in FIG. 10, the sheet of particulate asbestos-cementmaterial on the belt 42 passes continuously over a suction box 2 throughwhich a large portion of the water in the sheet is removed and thenmoves to the press section of the machine. Here the sheet is transferredfrom the belt 42 to the forming mandrel 94. The sheet from the belt isspirally wrapped and composited under pressure to form the tube 96. Thebelt after transferring the sheet to the mandrel 94 returns to thecylinder molds 40 and 50 after passing under the several tension andguide rollers and through the washers 98 and heater 100 and between thewringer rolls 102 where the belt again picks up a thin sheet ofasbestos-cement material.

The press section of the machine includes a heavy bottom anvil roll 104on which the forming mandrel rests during the formation of the tube 96.Acting upon the tube are two smaller press rolls 106 and 108 which arerotatably mounted on a frame (not shown) that is forced downwardly byhydraulic pressure. These rolls are permitted to rise as the thicknessof the tube increases, the pressure of the rolls being controlled bymeans of an automatic relief valve on the hydraulic medium. An endlessbelt 110 travels around the two press rolls 106- 108 and loops over asufficient number of guide and tension rolls to permit satisfactorymanipulating and intermittent cleaning thereof.

The foregoing explanation of the preferred embodiment of the inventionhas been directed primarily to the manufacture of asbestos-cement pipe.However, it is to be understood that the inventive concepts of theinstant application are equally applicable to systems for themanufacture of other asbestos-cement products such as sheets and board.Also, it is to be understood that the inventive concepts are readilyapplicable to any type of manufacture where a flocculating agent isutilized to aid 5 in the deposition of particulate material from aslurry onto a conveyor such as in the manufacture of asbestos orcellulosic paper. Also, although reference has been made to theparticular flocculating agent disclosed in Sfiscko et al., supra,because of the unique properties associated with these fiocculatingagents and asbestoscement, it is to be understood that the inventiveconcepts of the instant application are equally applicable with any typeof flocculating agent.

While the invention has been described in rather full detail, it will beunderstood that these details need not be strictly adhered to and thatvarious changes and modifications may suggest themselves to one skilledin the art, all falling within the scope of the invention as defined bythe subjoined claims.

What I claim is:

1. The method of controlling the thickness of a sheet of particulatematerial on a conveyor across the width of said conveyor comprising:

(a) containing. a slurry of particulate material in a vat,

(b) depositing portions of said particulate material from said slurryand forming on a conveyor a sheet of said particulate material acrossthe width of said conveyor wherein said conveyor has a Width extendingin the same direction as the Width of said vat,

(c) introducing an agent into said slurry at spaced locations across thewidth of said vat to control the rate of deposition of said particulatematerial from said vat onto said conveyor, and

(d) adjusting the space between said spaced locations where said agentis being introduced to control the rate of deposition of saidparticulate material from said slurry across the width of said vat andthe thickness of said sheet across the width of said conveyor.

2. The method of controlling the thickness of a sheet of particulatematerial on a. conveyor across the width of said conveyor comprising:

(a) containing a slurry of particulate material in a vat,

('0) depositing portions of said particulate material from said slurryand forming on a conveyor a sheet of said particulate material acrossthe width of said conveyor wherein said conveyor has a width extendingin the same direction as the width of said vat, (c) maintaining thelevel of said slurry in said v-at by flowing streams of slurry into saidvat at spaced locations across the width of said vat, and

(d) introducing an agent into some of said streams of slurry to controlthe rate of deposition of said particulate material from said slurryacross the width of said vat and the thickness of said sheet across thewidth of said conveyor.

3. The method as defined in claim 2 wherein said agent comprises:

(a) a flocculating agent.

4. In a method of producing asbestos-cement pipe hav- 60 ing goodstrength properties by:

(a) feeding a slurry comprising water and particulate materialcomprising asbestos and cement into a vat containing a rotary cylindermold, said rotary cylinder mold having a width extending in the samedirection as the width of said vat,

(b) depositing portions of said particulate material from said slurryonto said rotary cylinder mold and transferring said depositedparticulate material onto a conveyor to form a continuous sheet ofasbestoscement thereon,

(c) introducing an agent into said slurry to control the rate ofdeposition of said particulate material onto said rotary cylinder moldacross the width of said cylinder mold,

(d) winding said continuous sheet around a mandrel to form a pluralityof superposed layers of said sheet on said mandrel and applyingcompressive force to said superposed layers to consolidate them into ahandleable and principally uncured tubular asbestoscement article,

(e) removing said tubular asbestos-cement article from said mandrel, and

(f) curing said tubular asbestos-cement article to form a curedasbestos-cement pipe having good strength properties, the improvementcomprising:

(g) introducing said agent of step (c) into said slurry at spacedlocations across the Width of said vat, and

(h) adjusting the space between said spaced locations where said agentis being introduced to control the rate of deposition of saidparticulate material from said slurry across the width of said cylindermold and the thickness of said sheet across the width of said cylindermold.

5. Apparatus for controlling the thickness of a sheet of particulatematerial across the width thereof wherein said sheet is formed on aconveyor from a slurry of said particulate material comprising:

(a) a vat containing a slurry of particulate material,

(b) means for depositing portions of said particulate material from saidslurry and forming on a conveyor a sheet of said particulate materialacross the width of said conveyor,

(c) said conveyor having a width extending in the same directions as thewidth of said vat,

(d) means for controlling the rate of deposition of said particulatematerial from said slurry including the addition of an agent to saidslurry at spaced locations across the width of said vat, and

(e) means for adjusting the space between said spaced locations wheresaid agent is being introduced to control the rate of deposition of saidparticulate material from said slurry across the Width of said vat andthe thickness of said sheet across the Width of said conveyor.

6. Apparatus for controlling the thickness of a sheet of particulatematerial across the width thereof wherein said sheet is formed from aslurry of said particulate material comprising:

(a) a vat containing a slurry of particulate material,

(b) means for depositing portions of said particulate material acrossthe Width of said conveyor,

(c) said conveyor having a width extending in the same direction as thewidth of said vat,

((1) means for feeding a plurality of separate streams of slurry intosaid vat at spaced locations across the width of said vat to maintainthe level of said slurry in said vat,

(e) means for introducing an agent into some of said streams of slurryto control the rate of deposition of said particulate material onto saidconveyor, and

(f) means for adjusting the means in subparagraph (e) to select thestreams into which said agent is introduced to control the rate ofdeposition of said particulate material from said slurry across thewidth of said vat and the thickness of said sheet across the width ofsaid conveyor.

7. Apparatus as defined in claim 6 wherein said means for feeding aplurality of streams of slurry into said vat comprises:

(a) a flow pan having a length and width and a surface over which saidslurry may flow,

(b) means for dividing said surface of said flow pan into a plurality ofseparate channels,

(c) means for depositing said slurry onto the surface of said flow panso that said slurry is divided into portions with each portion moving asa stream through one of said channels, and

(d) means mounting said flow pan adjacent said vat so that said streamsof slurry fiow into said vat across the Width of said vat.

8. Apparatus as defined in claim 5, in which the means defined insub-section (b) comprise:

(a) rotatable cylinder mold in said vat for collecting portions of saidparticulate material from said slurry,

(b) said cylinder mold having a width extending in the same direction asthe Width of said vat, and

(c) means for transferring said deposited particulate material from saidcylinder mold onto said conveyor to form a sheet of said particulatematerial on said conveyor.

References Cited UNITED STATES PATENTS 1,872,480 8/1932 Manst 162-380 X2,182,353 12/1939 Rembert et al. l62154 X 2,983,383 5/1961 Wallace etal. M... 162336 X 3,095,346 6/1963 Sfiscko et al 162154 3,121,659 2/1964Amanzio 162-327 X S. LEON BASHORE, Primary Examiner.

1. THE METHOD OF CONTROLLING THE THICKNESS OF A SHEET OF PARTICULATEMATERIAL ON A CONVEYOR ACROSS THE WIDTH OF SAID CONVEYOR COMPRISING: (A)CONTAINING A SLURRY OF PARTICULATE MATERIAL IN A VAT, (B) DEPOSITINGPORTIONS OF SAID PARTICULATE MATERIAL FROM SAID SLURRY AND FORMING ON ACONVEYOR A SHEET OF SAID PARTICULATE MATIERAL ACROSS THE WIDTH OF SAIDCONVEYOR WHEREIN SAID CONVEYOR HAS A WIDTH EXTENDING IN THE SAMEDIRECTION AS THE WIDTH OF SAID VAT, (C) INTRODUCING AN AGENT INTO SAIDSLURRY AT SPACED LOCATIONS ACROSS THE WIDTH OF SAID VAT TO CONTROL THERATE OF DEPOSITION OF SAID PARTICULATE MATERIAL FROM SAID VAT ONTO SAIDCONVEYOR, AND (D) ADJUSTING THE SPACE BETWEEN SAID SPACED LOCATIONSWHERE SIAD AGENT IS BEING INTRODUCED TO CONTROL THE RATE OF DEPOSITIONOF SAID PARTICULATE MATERIAL FROM SAID SLURRY ACROSS THE WIDTH OF SAIDVAT AND THE THICKNESS OF SAID SHEET ACROSS THE WIDTH OF SAID CONVEYOR.5. APPARATUS FOR CONTROLLING THE THICKNESS OF A SHEET OF PARTICULATEMATERIAL ACORSS THE WIDTH THEREOF WHEREIN SAID SHEET IS FORMED ON ACONVEYOR FROM A SLURRY OF SAID PARTICULATE MATERIAL COMPRISING: (A) AVAT CONTAINING A SLURRY OF PARTICULATE MATERIAL, (B) MEANS FORDEPOSITING PORTIONS OF SAID PARTICULATE MATERIAL FROM SAID SLURRY ANDFORMING ON A CONVEYOR A SHEET OF SAID PARTICULATE MATERIAL ACROSS THEWIDTH OF SAID CONVEYOR, (C) SAID CONVEYOR HAVING A WIDTH EXTENDING INTHE SAME DIRECTION AS THE WIDTH OF SAID VAT, (D) MEANS FOR CONTROLLINGTHE RATE OF DEPOSITION OF SAID PARTICULATE MATERIAL FROM SAID SLURRYINCLUDING THE ADDITION OF AN AGENT TO SAID SLURRY AT SPACED LOCATIONSACROSS THE WIDETH OF SAID VAT, AND (E) MEANS FOR ADJUSTING THE SPACEBETWEEN SAID SPACED LOCATIONS WHERE SAID AGENT IS BEING INTRODUCED TOCONTROL THE RATE OF DEPOSITION OF SAID PARTICULATE MATERIAL FROM SAIDSLURRY ACROSS THE WIDTH OF SAID VAT AND THE THICKNESS OF SAID SHEETACROSS THE WIDTH OF SAID CONVEYOR.